Cup drawing die and method



ug. 6, 1968 M. BUSHI CUP DRAWING DIE AND METHOD 3 Sheets-Sheet l 'Filed Sept. 27, 1965 wllmbwml f m H la,

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Ag 6, 1963 M. Busi-u 3,395,562

CUP DRAWING DIE AND METHOD ATTORNEYS ug- 6, 1968 M. BUSHI 3,395,562

CUP DRAWING DIE AND METHOD Filed Sept. 27. 1965 5 Sheets-Sheet 3 INV EN TOR MICHAEL BUSH! M, Za/y @mul-@ ATTORNEYS United States 3,395,562 CUP DRAWING DIE AND METHOD Michael Bush, Cleveland, Ohio, assignor to The Quality Tool & Die Co., Cleveland, Ohio, a corporation of Ohio Filed Sept. 27, 1965, Ser. No. 490,415 Claims. (Cl. 72-350) ABSTRACT OF THE DISCLOSURE The present invention relates generally as indicated to a cup drawing die and method and more particularly to a die and method for drawing throw-away cups from thin strip material such as aluminum of .0035 thickness.

One prevalent use of cups drawn from such thin aluminum strip is in chemistry laboratories for analysis of chemical compositions. For throw-away use, the cups should be inexpensive and should be tapered so that the cups may be nested for compact shipment and storage and for ease of retrieval for use. Aside from the foregoing, cups drawn by the present die and method may have a multitude of uses as in connection with food preparation and vending viz., cupcakes, pies, gelatin molds, etc.

In the drawing of cups from thin strip metal as aforesaid, the wrinkling or pleating of the mouth of the cup is unavoidable and, in fact, uniform, ne wrinkling of the mouth of the cup is desirable to obviate cutting of the hands of the user thereof. However, a drawback of known dies and methods is that such wrinkling is non-uniform and, furthermore, despite the use of a tapered punch, the drawn articles will have large wrinkles adjacent the bottom of the cup which bulge outwardly to prevent proper nesting of the cups for shipment and storage, except by subsequent operations involving added labor and tooling.

Accordingly, it is a principal object of the present invention to provide a novel die and method for drawing cups from thin strip material which will have uniform, fine corrugations or wrinkles at the mouth thereof and which have uniform wrinkles adjacent the bottom of the cup which do not bulge as previously mentioned so that the cups formed by the present die and method will uniformly nest within one another without supplemental operations.

Other objects and advantages of the present invention will become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail a certain illustrative embodiment of the invention, this being indicative, however, of but one of the various ways in which the principle of the invention may be employed.

arent r 3,395,562 Patented Aug. 6, 1 968 ICC In said annexed drawings:

FIG. 1 is a front elevation view of a cup drawing press embodying the die and method herein;

FIG. 2 is a top plan view of FIG. l;

FIG. 3 is a cross-section view on enlarged scale taken substantially along the line 3 3, FIG. 1;

FIGS. 4 to 8 inclusive are -vertical cross-section views of a blanking and drawing die showing the successive steps in the formation of a cup from thin strip metal such as, for example, aluminum strip of .0035 thickness, FIG. 4 being a cross-section view, on enlarged scale, taken substantially along line 44, FIG. 3;

FIG. 9 is a side elevation View of a nested stack of cups formed by the present die and method; and

FIG. l0 is a perspective view of a cup shown with the tab thereof bent for grasping as by tongs for heating the contents thereof as over a Bunsen burner or the like.

Referring now more particularly to the drawings, and first to FIGS. '1, 2, and 3, the press 1 herein comprises a base 2 on which are mounted electrical and uid controls for automatic operation. For example, the reference numeral 3 designates an oil reservoir on which is mounted an electric motor-driven pump 4 for actuating a hydraulic cylinder 5 by operation of a conventional solenoid valve or the like. There is also provided a pneumatic cylinder 6 and likewise, suitable solenoid valves or the like may be employed for controlling actuation of said cylinder 6 and also another cylinder (not shown) for operating the strip feed mechanism 7. The cylinder 6 is mounted on a plate 8 which is supported by posts 9. No attempt is herein made to illustrate or describe in detail the electric or fiuid piping circuits, since once it has been determined what movements are desired or necessary persons skilled in the art may readily provide for automatic operation through judiciously located limit switches and control circuits.

Accordingly, the description herein will be directed principally to the blanking and drawing die assembly which is mounted on said base 2, the same comprising a bottom shoe or plate 10 and a top plate 11 bolted together and held in parallel spaced relation by spacers \12. Mounted on the bottom plate 10 is a punch pad 14 which, at each of three locations has projecting upwardly therefrom a combination blanking punch and drawing die 15. Each die 15 has an upper plane annular face, the periphery of which is of the shape shown in FIG. 2 for cutting from the strip stock S a circular blank having a radially extending tab. See also FIG. 3 for the preferred arrangement of three of said dies 15. Superimposed on said punch pad 14 is a stripper 16 mounted as on stripper bolts 17 and having springs 18 operative to yieldably urge said stripper 116 upwardly against the heads of bolts 17 so that its upper face is coplanar with the upper face of said die 15 when the press 1 is open.

Vertically reciprocably mounted as on the rods 19 is an upper die plate 20 which has mounted on the underside thereof blanking dies 21 each coaxially aligned with the punch portion of a corresponding die '15. The die plate 20 is vertically moved as by means of the hydraulic cylinder 5, the piston rod (not shown) of which is connected to the center of the plate 20.

Within each blanking die 21 is a pair of concentric pressure rings 23 and 24, the outer one 23 of which is more firmly pressed against the blank B (see FIGS. 4 to 8) by the springs 25 than is the inner ring 24 by the springs 26.

Vertically reciprocable within the respective blanking dies 21 are drawing punches 30 which are joined together at their upper ends by a plate 31, said plate 31, in turn, being connected to the piston rod (not shown) of the pneumatic cylinder 6.

As will hereinafter be explained in detail, each said combination Iblanking and drawing die 15 is internally grooved and has therein an expansible ring 32 comprising a plurality of segments 33 which are held together as shown in FIG. 4, as by means of a garter spring or elastic ring such as an O-ring 34 of rubber-like material.

With reference to the stock feed unit 7, this may be of more or less conventional form arranged to predeterminedly advance the strip stoc-k S after each stroke of the press 1 and preferably the stock S is supplied from a roll R which may be driven at a uniform speed to provide a stock festoon or loop to permit incremental advance of the stock S during the operation of the press 1, and thus to maintain substantially constant tension on the stock S. Of course, if desired, the stock feed roll R may be periodically driven to provide along loop of stock for permitting several strokes of the press before the stock feed roll is again driven. Each time that the press 1 opens the feed mechanism 7 will be actuated to grip the stock S and advance it a predetermined amount between the stripper 16 and the guide plate 35.

Referring now to operation of the press 1 herein, when the stock S is positioned in the press as shown in FIG. 4, the hydraulic cylinder will be actuated to move the die plate 2t) down to the position shown in FIG. 5, and thus the blanking die 21 in cooperation with die 15 cuts a blank B from the stock S, and, at the same time, the pressure rings 23 and 24 will frictionally engage the peripheral portion of the blank B with differential pressure as aforesaid, the greater pressure being on the outer annular portion than on the adjacent inner annular portion. Thereafter, the pneumatic cylinder 6 will be actuated to cause the drawing punch 30 to be moved downwardly as successively shown in FIGS. 6, 7, and 8. FIG. 6 shows the blank B as partially formed while the peripheral portion was held by both pressure rings 23 and 24, and when the punch 30 reaches the FIG. 6 position, the peripheral portion of the blank B is gripped only by the low pressure ring 24 and the segments 33 are just engaging the periphery of the bottom of the blank B. In FIG. 7 the punch 30 has moved down so that the segments 33 have already flattened or ironed the bulges 36 (see FIG. 9) adjacent the bottom of the blank B and are now pressing or ironing the ne side wrinkles 37 against the side tapered portion 38 of the punch 30. In FIG. 8 the punch 30 has moved down to complete the drawing operation of the blank and the upper edge 39 of the drawn cup C is below the stripping ledge 40 whereby, when the punch 30 is moved upwardly from the FIG. 8 position to the FIG. 4 position, the finished cup C will be stripped therefrom and will drop down through the bottom plate onto the inclined discharge chute 41. The cups C collected at the end of the chute 41 will be stacked as shown in FIG. 9, and placed in cardboard tubes or the like, the tabs 42 being left in the drawn position shown in FIG. 9. In the event that the stripping ledge 40 does not operate to so strip the drawn cup C from the punch 30, the segments 33 will perform that function as the punch 30 continues to move upwardly.

When the drawn cups C herein are used the tabs 42 will be bent as shown in FIG. l0, so that they may be grasped as by suitable tongs 43.

When the hydraulic cylinder 5 is actuated to raise the die plate 20, the springs and 26 will urge the respective rings 23 and 24 to positions flush 'with the bottom plane faces of the blanking dies 21 and the springs 118 will move the stripper 16 upwardly to the position shown in FIG. 4 thus to strip the blanked stock S from the dies 15. Thereupon, the stock S will again be advanced by feed mechntSm 7 to repeat the aforesaid operations.

It has been found that if only a single pressure ring 23 or 24 were provided the pressure exerted thereby against the stock S would either be insufiicient for the initial portion (FIG. 5 to FIG. 6) of the drawing operation or excessive for final portion (FIG. 6 to FIG. 7) of the drawing operati-on. Accordingly, with the present die and method, the initial portion of the drawing operation is performed with high pressure exerted by ring 23 and the final portion of the drawing operation is performed with lower pressure exerted by ring 24. Furthermore, if it were attempted to draw a tapered cup C using a cylindrical die and a tapered punch, the portion of the cup adjacent the bottom would bulge to such an extent that the cups C could not be nested to any substantial degree within one another. This would entail extra lalbor and tooling for nesting the cups C into one another. With the present die and method, there is obtained proper flattening or ironing of the bulges adjacent the bottom of the cup and, at the same time, the wrinkles around the mouth of the cup C are uniform and tine so that a person using the cup C will not cut his hand or fingers.

It is to 'be noted that the annular lip 45 in the die 15 overlaps a shoulder on each of the segments 33 thus serving to center the ring 32 when it is in the contracted -position shown in FIGS. 4 and 5. Furthermore, the punch 30 has a cam surface 46 adjacent the base of the tapered end portion 38 which (just after the FIG. 7 position) engages the segments 33 of ring 32 to expand them away from the mouth of the cup C. In this way, the cup C at its mouth will have a thickness of from about .015 to about .020 without excessive ironing or wiping to .00 or less thickness as would otherwise occur in the absence of cam surface 46.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims, or the equivalent of such, be employed.

I particularly point out and distinctly claim as my invention:

1. A press for drawing thin wall tapered cups and the like comprising an annular drawing die having a radially yieldable portion; holding means yieldably peripherally holding a die blank against said drawing die; a punch having a tapered end portion coaxial with said drawing die; and means for moving said punch axially through said drawing die thus to draw the blank to cup form; said yieldable portion of said drawing die comprising plural ring segments disposed in an internal groove in said drawing die and a spring ring around said segments urging said segments radially inward, said drawing die having an annular lip which overlaps a shoulder on each of said segments for centering said segments in their radially innermost position; said segments being operative to press the blank against the tapered end portion of said punch as the latter is moved through said drawing die.

2. The press of claim 1 wherein said holding means comprises concentric inner and outer rings, and spring means for pressing said outer ring with greater force than said inner ring towards said drawing die.

3. The press of claim 1 further comprising an internal stripping ledge on said drawing die adapted to engage the upper edge of the formed cup to strip the same from said punch during retraction of said punch from said drawing die.

4. The press of claim 1 wherein said punch has a cam means thereon adjacent the base of said tapered end portion for engaging said segments to force said segments away from the blank near the end of the draw forming operation to prevent excessive ironing and wiping of the lip of the cup.

S. The press of claim 1 further comprising an outer peripheral cutting edge on said drawing die; a blanking die coaxial with said drawing die and provided with an inner peripheral cutting edge; means for axially moving said blanking die to a position around said drawing die thus 5 6 to cut the die blan-k from strip material inserted between 1,534,698 4/ 1925 Gansert et a1 72-57 said dies; and means for stripping the strip material fram 1,617,547 2/ 1927 Schneider 72-350 said drawing die in response to retraction of said punch 2,017,054 10/ 1935 Bruun 72-348 from said drawmg die. 5 FOREIGN PATENTS References Cited 63,081 1/ 1945 Denmark.

UNITED STATES PATENTS RICHARD I. HERBST, Primary Examiner. 1,011,193 12/1911 Hackney 72-347 

